Ladybugs: Warm-weather guests that are more like pests

Saturday

Oct 31, 2009 at 12:01 AM

My wife Kris and I have an older, Victorian home. We recently had the white, aluminum exterior power-washed. It looked great. Days later, when cooler temperatures rebounded unto the 70s, I noticed that the house was covered with hundreds, or dare I say, thousands of moving beetles. Upon closer inspection, I found them to be ladybugs; multicolored Asian lady beetles, MALBs), Harmonia axyridis Pallas) to be scientifically precise.

GEORGE P. LESHANSKI

My wife Kris and I have an older, Victorian home. We recently had the white, aluminum exterior power-washed. It looked great. Days later, when cooler temperatures rebounded unto the 70s, I noticed that the house was covered with hundreds, or dare I say, thousands of moving beetles. Upon closer inspection, I found them to be ladybugs; multicolored Asian lady beetles, MALBs), Harmonia axyridis Pallas) to be scientifically precise. That evening, beetles put on an aerial show in our kitchen, flitting from light fixtures onto the walls, curtains and the television screen. The beetles also appeared in an upstairs bathroom.

Who are these home invaders and what can we do about them?

Most gardeners know that ladybugs are beneficial insects. Ladybugs are beetles of the tree-dwelling family Coccinellidae. They were introduced to the state in 1978 and 1981 by the U.S. Department of Agriculture as biological control agents, to supplement the good work done by the native lady beetles, both feast on aphids and scale insects.

Initially, the Asian beetle did not fare well in cold weather. The first record of their overwintering was in 1993, the year adult lady beetles were first found congregating on windows, doors, porches and decks, seeking shelter for the coming cold weather. They have since become a homeowner nuisance wherein they occupy residences from September through April.

The multicolored Asian lady beetles are slightly bigger than native lady beetles, are oval or convex in shape, yellow to red in color, and sometimes display black spots on their wing covers. Adults can live for more than a year. The beetle's gestation cycle from egg to adult to egg is about 25 days depending on conditions. Eggs are laid on the underside of low-growing plants and hatch a few days after. For about two weeks, the larvae feed on aphids. The adults emerge several days after pupation.

In October on a warm, sunny afternoon following a cold night, the lady beetles congregate outside houses and other buildings, seeking out winter shelter, apparently attracted to the sunlight reflecting off south of south-west sides of buildings. The aggregate population overwinters, but do not mate until the next spring.

Once inside a warm house the beetles move toward light. With tens of thousands congregating at one time in attics, ceilings and walls, it is not surprising that some will find their way into living quarters, with annoying consequences. From experience, I can vouch that when threatened, they give off a nasty smelling defensive chemical, which can cause spotting on walls and other surfaces. Our two dogs, who typically enjoy playing with any bugs they find crawling on the floor, zealously avoid lady beetles.

There are reports that people have been bitten by lady beetles, and some individuals have experienced allergic reactions to the beetles' defensive excretions: sinus and mild skin irritations. It is suggested that you wash your hands and all skin which has come into contact with the beetles.

The best way to control an infestation is to prevent the beetles from entering your home: much easier said than done, when your house is over 100 years old and covered with loose-fitting siding. But for those with homes where exclusion is possible, seal cracks around doors, windows, utility pipes and all other openings with a good quality silicone or silicone latex caulk. Other openings such as chimneys and exhaust vents can be covered with Number 20, or smaller mesh screens.

During the winter months, infected households should expect several visits a day from the lady beetles, usually in the same locations. If the number of beetles becomes too much to bear, try to figure out where in the affected room they are coming from. Seal the likely entrances with caulk or tape and you should cut down on the problem.

I have found that the best way to get rid of them is with a vacuum cleaner suction attachment, or a bug vacuum. Note that when using a bug vacuum, emptying the bag after each use will minimize the foul-smelling secretions.

If you are not satisfied with the vacuum system, you could try a light trap. These are available from pest control or pest supply companies. Select the model utilizing a sticky glue base as opposed to the "bug zapper" types, as the latter do not work inside the home where there are many competing light sources. The glue traps are easy to remove and dispose of.

While it is theoretically possible to apply insecticide on an entire house, or its south and southwest facing exposures, it would require multiple applications to be effective, and is an impractical solution for ladybugs.

The recommended application should only be applied by licensed pest-control operators in late September or early October. However, the insecticide quickly breaks down and may become ineffective after as little time as week.

I would not recommend using insecticide for them, while it might kill thousands of the beetles, it could invite another pest, the carpet beetle to feed on the dead beetles. Once that menu item is exhausted, they might turn to other delectable items such as wool items, stored dry goods or other animal products. If the infestation becomes untenable, you can hire a qualified licensed pesticide applicator.

Penn State Master Gardeners provide garden assistance to the general public on Mondays from 10 a.m. to noon. If you have a gardening question at another time you can e-mail them at Monroemg@psu.edu or call 570) 421-6430 and request to leave a voice-mail message. Please include your full name, mailing address, phone number and e-mail address, along with a detailed message.

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